The purpose of this research is to elucidate the mechanisms that regulate adrenal catecholamine synthesis and secretion. Catecholamine synthesis and secretion will be studied in suspensions of pheochromocytoma cells and of normal chromaffin cells. I have recently developed a method for the on-line monitoring of catecholamine secretion from superfused chromaffin cells. With this method, I will study the kinetics of catecholamine secretion, and the desensitization and recovery of the secretory response to acetylcholine and to other stimuli. I have also developed a method for measuring the activity of tyrosine 3-monooxygenase (tyrosine hydroxylase) in intact chromaffin cells. In this method, cells are incubated with tyrosine, and the rate of production of dihydroxyphenylalanine is measured by liquid chromatography with electrochemical detection. I will use this method to study the coordinate regulation of catecholamine secretion and of tyrosine hydroxylase activity. In particular, I will examine the roles of cyclic adenosine 3':5'-monophosphate and of Ca ion in these processes. I will also study the effects of ionophores, such as lasalocid and monensin, on these processes. Finally, I will investigate the role of adenosine in the regulation of adenylate cyclase activity and tyrosine hydroxylase activity in chromaffin cells.